U.S. patent application number 09/983972 was filed with the patent office on 2002-06-20 for thin film magnetic head and method of manufacturing the same.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Terunuma, Koichi.
Application Number | 20020075609 09/983972 |
Document ID | / |
Family ID | 18807495 |
Filed Date | 2002-06-20 |
United States Patent
Application |
20020075609 |
Kind Code |
A1 |
Terunuma, Koichi |
June 20, 2002 |
Thin film magnetic head and method of manufacturing the same
Abstract
Provided are a thin film magnetic head and a method of
manufacturing the same, which can prevent an output decrease
without impairment of productivity and other characteristics, while
adapting to an increase in a recording density. In the thin film
magnetic head, an MR film is sandwiched in between first and second
gap films having electrical insulating properties, which are
sandwiched in between first and second shield layers. The first
shield layer has an inner layer and an outer layer laminated in
order from the MR film, and the second shield layer has an inner
layer and an outer layer laminated in order from the MR film. The
respective inner layers of the first and second shield layers have
hardness higher than that of the respective outer layers thereof so
as to prevent the first and second shield layers from
deforming.
Inventors: |
Terunuma, Koichi; (Tokyo,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
TDK CORPORATION
Tokyo
JP
103-8272
|
Family ID: |
18807495 |
Appl. No.: |
09/983972 |
Filed: |
October 26, 2001 |
Current U.S.
Class: |
360/319 ;
29/603.16; G9B/5.087; G9B/5.116 |
Current CPC
Class: |
G11B 5/3133 20130101;
G11B 5/3903 20130101; B82Y 10/00 20130101; Y10T 29/49048
20150115 |
Class at
Publication: |
360/319 ;
29/603.16 |
International
Class: |
G11B 005/39 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2000 |
JP |
2000-331088 |
Claims
What is claimed is:
1. A thin film magnetic head comprising: a functional film having a
magnetic transducer function; a first gap film and a second gap
film sandwiching the functional film in between, the first and
second gap films each having electrical insulating properties; and
a first shield layer and a second shield layer sandwiching the
functional film with the first and second gap films in between,
respectively, so as to prevent an undesired magnetic field from
reaching to the functional film, wherein at least one of the first
and second shield layers has an inner layer and an outer layer
laminated in order from the functional film, and the inner layer
has a hardness higher than that of the outer layer.
2. A thin film magnetic head according to claim 1, wherein the
first shield layer has the inner layer and the outer layer, and the
sum of a thickness of the inner layer of the first shield layer and
a thickness of the first gap film is equal to or more than 40
nm.
3. A thin film magnetic head according to claim 1, wherein the
second shield layer has the inner layer and the outer layer, and
the sum of a thickness of the inner layer of the second shield
layer and a thickness of the second gap film is equal to or more
than 40 nm.
4. A thin film magnetic head according to claim 2, wherein the
second shield layer has the inner layer and the outer layer, and
the sum of a thickness of the inner layer of the second shield
layer and a thickness of the second gap film is equal to or more
than 40 nm.
5. A thin film magnetic head according to claim 1, wherein a
Vickers hardness of the inner layer is equal to or higher than
500.
6. A thin film magnetic head according to claim 2, wherein a
Vickers hardness of the inner layer is equal to or higher than
500.
7. A thin film magnetic head according to claim 3, wherein a
Vickers hardness of the inner layer is equal to or higher than
500.
8. A thin film magnetic head according to claim 4, wherein a
Vickers hardness of the inner layer is equal to or higher than
500.
9. A thin film magnetic head according to claim 1, wherein the
thickness of the inner layer is equal to or less than 300 nm.
10. A thin film magnetic head according to claim 2, wherein the
thickness of the inner layer is equal to or less than 300 nm.
11. A thin film magnetic head according to claim 3, wherein the
thickness of the inner layer is equal to or less than 300 nm.
12. A thin film magnetic head according to claim 4, wherein the
thickness of the inner layer is equal to or less than 300 nm.
13. A thin film magnetic head according to claim 5, wherein the
thickness of the inner layer is equal to or less than 300 nm.
14. A thin film magnetic head according to claim 6, wherein the
thickness of the inner layer is equal to or less than 300 nm.
15. A thin film magnetic head according to claim 7, wherein the
thickness of the inner layer is equal to or less than 300 nm.
16. A thin film magnetic head according to claim 8, wherein the
thickness of the inner layer is equal to or less than 300 nm.
17. A thin film magnetic head according to claim 1, wherein the
outer layer is made of a material containing nickel (Ni) and iron
(Fe).
18. A thin film magnetic head comprising: a functional film having
a magnetic transducer function; a first insulating film and a
second insulating film sandwiching the functional film in between;
and a first magnetic layer and a second magnetic layer sandwiching
the functional film with the first and second insulating films in
between, respectively, wherein at least one of the first and second
magnetic layers has an inner layer and an outer layer laminated in
order from the functional film, and the inner layer has a hardness
higher than that of the outer layer.
19. A method of manufacturing a thin film magnetic head including a
functional film having a magnetic transducer function and a first
shield layer and a second shield layer for preventing an undesired
magnetic field from reaching to the functional film, comprising the
steps of: forming the first shield layer on a base with an
insulating layer in between; forming a first gap film having
electrical insulating properties on the first shield layer; forming
the functional film on the first gap film; forming a second gap
film having electrical insulating properties on the functional
film; and forming the second shield layer on the second gap film,
wherein in at least one of the step of forming the first shield
layer and the step of forming the second shield layer, at least one
of the first and second shield layers is formed so as to have an
inner layer and an outer layer laminated in order from the
functional film, and so that the inner layer has a hardness higher
than that of the outer layer.
20. A method of manufacturing a thin film magnetic head according
to claim 19, wherein the step of forming the first shield layer
includes the step of forming the outer layer by means of plating,
and the step of forming the inner layer on the outer layer by means
of sputtering.
21. A method of manufacturing a thin film magnetic head according
to claim 19, wherein the step of forming the second shield layer
includes the step of forming the inner layer by means of
sputtering, the step of forming a seed layer which is a part of the
outer layer on the inner layer by means of sputtering, and the step
of forming the remaining part of the outer layer by means of
plating using the seed layer as an electrode.
22. A method of manufacturing a thin film magnetic head according
to claim 20, wherein the step of forming the second shield layer
includes the step of forming the inner layer by means of
sputtering, the step of forming a seed layer which is a part of the
outer layer on the inner layer by means of sputtering, and the step
of forming the remaining part of the outer layer by means of
plating using the seed layer as an electrode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a thin film magnetic head for use
in a magnetic recording apparatus or the like such as a hard disk
drive, and a method of manufacturing the same.
[0003] 2. Description of the Related Art
[0004] Recently, an improvement in performance of a thin film
magnetic head has been sought in accordance with an increase in an
areal recording density of a hard disk or the like. A composite
thin film magnetic head, which has a laminated structure comprising
a reproducing head having a magnetoresistive element (hereinafter
referred to as an MR element) and a recording head having an
inductive magnetic transducer, is widely used as the thin film
magnetic head. The MR element has a single-layer or multilayer
magnetoresistive film (hereinafter referred to as an MR film) which
is sensitive to a signal magnetic field so as to exhibit a
resistance change, and thus the MR film is adapted to read out
information according to the resistance change of the MR film. As
MR films, known are an AMR film exhibiting an anisotropic
magnetoresistive effect (an AMR effect) and a GMR film exhibiting a
giant magnetoresistive effect (a GMR effect).
[0005] The thin film magnetic head is formed on a block-shaped
slider for moving along a recording surface of a magnetic medium,
so as to be directly faced with the magnetic medium. A facing
surface (hereinafter referred to as an air bearing surface) to be
faced with the magnetic medium is obtained by polishing the thin
film magnetic head together with the slider.
[0006] In general, many data elements (each of which is an area
corresponding to 1 bit of information) are arranged on a track line
formed on the magnetic medium, and a distance between the data
elements is very short. Thus, when reading information of one data
element, the MR film of the thin film magnetic head has to avoid
being affected by magnetic fields of other data elements adjacent
to the data element. Therefore, the thin film magnetic head has a
structure such that the MR film is sandwiched in between a pair of
shield layers having high magnetic permeability. A distance between
the shield layers substantially corresponds to the distance between
the data elements.
[0007] In accordance with a recent increase in the areal recording
density of the hard disk or the like, it is required that the
distance between the shield layers of the thin film magnetic head
be further reduced in order to increase an arrangement density
(i.e., a linear density) of the data elements on the track line. It
is required that the distance between the shield layers be reduced
to 80 nm or less in order to achieve the areal recording density in
excess of 30 Gbit/inch.sup.2 (4.7 Gbit/cm.sup.2), for example.
[0008] However, such a reduction in the distance between the shield
layers may cause the shield layers to deform and thus come into
contact with the MR film, when the slider and the thin film
magnetic head are polished to form the air bearing surface. In this
case, a problem exists: that is, a short circuit occurs between
each shield layer and the MR film, and thus, during the reading of
information, a part of a sense current to pass through the MR film
passes through the shield layers, so that this leads to an output
decrease.
[0009] In order to prevent such a contact of the shield layers with
the MR film, it is possible that the shield layers are made of a
deformation-resistant material, namely, a material having high
hardness. For example, in Unexamined Japanese Patent Application
Publication No. Hei 2-116009, it is proposed that a shield layer is
made of FeAlSi (sendust). Moreover, in Unexamined Japanese Patent
Application Publication No. Sho 60-239911, it is proposed that a
shield layer is made of an amorphous magnetic alloy. Furthermore,
in Unexamined Japanese Patent Application Publication No. Hei
6-195643, it is proposed that a shield layer is made of an alloy
made of Fe, N (nitrogen) and M (Ta (tantalum), Hf (hafnium) or the
like).
[0010] However, the following problems in manufacturing exist when
the shield layers are made of the material having high hardness as
mentioned above. That is, one problem is as follows. Generally, the
shield layers are formed by means of sputtering and are then
patterned by use of ion milling or the like, and thus, when the
shield layers are made of the above-mentioned material having high
hardness, patterning requires long-time ion milling, which leads to
deterioration in productivity. Another problem is as follows: that
is, any of the above-mentioned materials having high hardness has
low thermal conductivity and thus cannot efficiently diffuse heat
generated by the MR film, so that this leads to a rise in
temperature of the MR film.
SUMMARY OF THE INVENTION
[0011] The invention is designed to overcome the foregoing
problems. It is an object of the invention to provide a thin film
magnetic head and a method of manufacturing the same, which are
capable of adapting to an increase in a linear recording density
and also capable of preventing an output decrease without
impairment of productivity and other characteristics.
[0012] A thin film magnetic head of the invention comprises: a
functional film having a magnetic transducer function; a first gap
film and a second gap film sandwiching the functional film in
between, the first and second gap films each having electrical
insulating properties; and a first shield layer and a second shield
layer sandwiching the functional film with the first and second gap
films in between, respectively, so as to prevent an undesired
magnetic field from reaching to the functional film, wherein at
least one of the first and second shield layers has an inner layer
and an outer layer laminated in order from the functional film, and
the inner layer has a hardness higher than that of the outer
layer.
[0013] In the thin film magnetic head of the invention, at least
one of the first and second shield layers has the inner layer
having higher hardness close to the functional film. In the step of
polishing a magnetic-field-facing surface of the thin film magnetic
head, the existence of the inner layer allows at least one of the
first and second shield layers to become resistant to deformation.
Therefore, this allows preventing a contact of at least one of the
first and second shield layers with the functional film and thus
permits preventing an output decrease of the thin film magnetic
head, even when a distance between the first and second shield
layers is reduced in order to increase a linear recording density.
Furthermore, at least one of the first and second shield layers has
the outer layer having lower hardness than the hardness of the
inner layer, and therefore the shield layer is patterned in a
shorter time by means of ion milling or the like, as compared to a
shield layer made of only a material having high hardness.
[0014] In the thin film magnetic head of the invention, when the
first shield layer has the inner layer and the outer layer, it is
preferable that the sum of a thickness of the inner layer of the
first shield layer and a thickness of the first gap film be equal
to or more than 40 nm. When the second shield layer has the inner
layer and the outer layer, it is preferable that the sum of a
thickness of the inner layer of the second shield layer and a
thickness of the second gap film be equal to or more than 40 nm.
Preferably, a Vickers hardness of the inner layer is equal to or
higher than 500. Preferably, the thickness of the inner layer is
equal to or less than 300 nm. Preferably, the outer layer contains
Ni and Fe.
[0015] Another thin film magnetic head of the invention comprises:
a functional film having a magnetic transducer function; a first
insulating film and a second insulating film sandwiching the
functional film in between; and a first magnetic layer and a second
magnetic layer sandwiching the functional film with the first and
second insulating films in between, respectively, wherein at least
one of the first and second magnetic layers has an inner layer and
an outer layer laminated in order from the functional film, and the
inner layer has a hardness higher than that of the outer layer.
[0016] A method of manufacturing a thin film magnetic head of the
invention including a functional film having a magnetic transducer
function and a first shield layer and a second shield layer for
preventing an undesired magnetic field from reaching to the
functional film comprises the steps of forming the first shield
layer on a base with an insulating layer in between; forming a
first gap film having electrical insulating properties on the first
shield layer; forming the functional film on the first gap film;
forming a second gap film having electrical insulating properties
on the functional film; and forming the second shield layer on the
second gap film, wherein in at least one of the step of forming the
first shield layer and the step of forming the second shield layer,
at least one of the first and second shield layers is formed so as
to have an inner layer and an outer layer laminated in order from
the functional film, and so that the inner layer has a hardness
higher than that of the outer layer.
[0017] In the method of manufacturing a thin film magnetic head of
the invention, obtained is a thin film magnetic head in which at
least one of the first and second shield layers has the inner layer
having higher hardness close to the functional film.
[0018] In the method of manufacturing a thin film magnetic head of
the invention, when the first shield layer has the inner layer and
the outer layer, it is preferable that the step of forming the
first shield layer include the step of forming the outer layer by
means of plating and the step of forming the inner layer on the
outer layer by means of sputtering. When the second shield layer
has the inner layer and the outer layer, it is preferable that the
step of forming the second shield layer include the step of forming
the inner layer by means of sputtering, the step of forming a seed
layer which is a part of the outer layer on the inner layer by
means of sputtering, and the step of forming the remaining part of
the outer layer by means of plating using the seed layer as an
electrode.
[0019] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a perspective view of an outside shape of a
rotating arm on which a thin film magnetic head according to an
embodiment of the invention is mounted;
[0021] FIG. 2 is a perspective view of an outside shape of a slider
on which the thin film magnetic head according to the embodiment of
the invention is formed;
[0022] FIG. 3 is an exploded perspective view of a structure of the
thin film magnetic head according to the embodiment of the
invention;
[0023] FIG. 4 is a plan view showing a planar shape of the thin
film magnetic head shown in FIG. 3;
[0024] FIG. 5 is a cross sectional view showing a sectional
structure of the thin film magnetic head shown in FIG. 3, showing a
cross section perpendicular to an air bearing surface;
[0025] FIG. 6 is a cross sectional view showing a sectional
structure of the thin film magnetic head shown in FIG. 3, showing a
cross section parallel to the air bearing surface;
[0026] FIG. 7 is an enlarged sectional view of a structure of an MR
element of the thin film magnetic head shown in FIG. 3;
[0027] FIG. 8 is a cross sectional view for describing a step of a
method of manufacturing the thin film magnetic head shown in FIG.
3;
[0028] FIG. 9 is a cross sectional view for describing a step
following the step shown in FIG. 8;
[0029] FIG. 10 is a cross sectional view for describing a step
following the step shown in FIG. 9;
[0030] FIG. 11 is a cross sectional view for describing a step
following the step shown in FIG. 10;
[0031] FIG. 12 is a cross sectional view for describing a step
following the step shown in FIG. 11;
[0032] FIG. 13 is a cross sectional view for describing a step
following the step shown in FIG. 12;
[0033] FIG. 14 is a cross sectional view for describing a step
following the step shown in FIG. 13;
[0034] FIG. 15 is a cross sectional view for describing a step
following the step shown in FIG. 14;
[0035] FIG. 16 is a cross sectional view showing a sectional
structure of a thin film magnetic head according to a modified
embodiment; and
[0036] FIG. 17 is a plot of the results of measurement of fraction
defective of examples of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] <Configuration of Magnetic Head Slider>
[0038] Firstly, a structure of a thin film magnetic head 1
according to an embodiment of the invention will be described with
reference to FIGS. 1 to 7.
[0039] FIG. 1 shows a configuration of a rotating arm 8 comprising
the thin film magnetic head 1 according to the embodiment. The
rotating arm 8 is used in, for example, a hard disk drive (not
shown) or the like and has a slider 2 on which the thin film
magnetic head 1 (see FIG. 2) is formed. For instance, the slider 2
is mounted on the tip of an arm 8A which is rotatably supported by
a pivot 8B. For example, the arm 8A is rotated by driving force of
a voice coil motor (not shown), and thus the slider 2 moves in a
direction X in which the slider 2 crosses a track line along a
recording surface of a magnetic medium 3 such as a hard disk (a
lower surface of the recording surface in FIG. 1). For example, the
magnetic medium 3 rotates in a direction Z substantially
perpendicular to the direction X in which the slider 2 crosses the
track line.
[0040] FIG. 2 shows a configuration of the slider 2 shown in FIG.
1. The slider 2 has a block-shaped base 2D made of
Al.sub.2O.sub.3--TiC (alumina titanium carbide), for example. The
base 2D is, for instance, substantially hexahedral in shape, and
one surface of the base 2D closely faces the recording surface of
the magnetic medium 3 (see FIG. 1). The surface facing the
recording surface of the magnetic medium 3 is called an air bearing
surface (ABS) 2E, which includes a slider rail 2A having a
predetermined shape. The thin film magnetic head 1 is provided on
one side of the base 2D (the left side in FIG. 2) faced with the
air bearing surface 2E.
[0041] FIG. 3 shows an exploded view of a configuration of the thin
film magnetic head 1. FIG. 4 shows a planar structure viewed in the
direction of the arrow IV of FIG. 3. FIG. 5 shows a sectional
structure viewed in the direction of the arrows along the line V-V
of FIG. 4. FIG. 6 shows a sectional structure viewed in the
direction of the arrows along the line VI-VI of FIG. 4. The thin
film magnetic head 1 has an integrated structure comprising a
reproducing head 1A for reproducing magnetic information recorded
on the magnetic medium 3 and a recording head 1B for recording
magnetic information on the magnetic medium 3.
[0042] As shown in FIGS. 3 and 5, the reproducing head 1A has a
laminated structure comprising an insulating layer 11, a first
shield layer 12, a first gap film 13, a second gap film 14, a
second shield layer 15 and an insulating layer 16, which are
laminated in this order on the base 2D. For example, the insulating
layer 11 is 2 .mu.m to 10 .mu.m in thickness in a laminating
direction (hereinafter referred to as a thickness) and is made of
Al.sub.2O.sub.3 (aluminum oxide).
[0043] For example, each of the first and second shield layers 12
and 15 is 1 .mu.m to 3 .mu.m in thickness and is made of a magnetic
material having high magnetic permeability. The first and second
shield layers 12 and 15 function to prevent an undesired magnetic
field from reaching to an MR film 20. Each of the first and second
shield layers 12 and 15 has a planar shape shown in FIG. 3. In the
embodiment, the first shield layer 12 corresponds to a specific
example of "a first shield layer" or "a first magnetic layer" of
the invention. The second shield layer 15 corresponds to a specific
example of "a second shield layer" or "a second magnetic layer" of
the invention.
[0044] As shown in FIG. 6, the first gap film 13 and the second gap
film 14 are sandwiched in between the first shield layer 12 and the
second shield layer 15, and the MR film 20 is sandwiched in between
the first gap film 13 and the second gap film 14. The first shield
layer 12 has an inner layer 12B and an outer layer 12A, which are
located far from and close to the first gap film 13, respectively,
and the inner layer 12B has a hardness higher than that of the
outer layer 12A. On the other hand, the second shield layer 15 has
an inner layer 15B and an outer layer 15A in order from the second
gap film 14, and the inner layer 15B has a hardness higher than
that of the outer layer 15A.
[0045] The outer layer 12A of the first shield layer 12 and the
outer layer 15A of the second shield layer 15 are made of a
magnetic material having high magnetic permeability in particular,
e.g., NiFe (a nickel-iron alloy), because NiFe has high magnetic
permeability and thus has a great effect in preventing an undesired
magnetic field from reaching to the MR film 20 (the so-called
shield effect). Moreover, NiFe has high thermal conductivity and
thus has the advantage of being capable of efficiently dissipating
heat generated by the MR film 20. More specifically, it is
preferable to use NiFe in which the percentage of content of Ni is
about 80 atom % and the percentage of content of Fe is about 20
atom % (hereinafter referred to as Ni.sub.80Fe.sub.20). An optimum
thickness of the outer layers 12A and 15A is 0.5 .mu.m to 5.0
.mu.m.
[0046] The inner layer 12B of the first shield layer 12 and the
inner layer 15B of the second shield layer 15 are made of a
magnetic material having a hardness higher than that of the outer
layer 12A and the outer layer 15A. For example, when the outer
layers 12A and 15A are made of Ni.sub.80Fe.sub.20, their Vickers
hardness Hv is about 250, and thus the inner layers 12B and 15B are
made of a magnetic material whose Vickers hardness Hv is higher
than 250, because this material allows the first and second shield
layers 12 and 15 to become resistant to deformation in the step of
polishing the air bearing surface 2E to be described later.
Preferably, the Vickers hardness Hv of the inner layers 12B and 15B
is, in particular, 500 or higher, because this can further ensure
that the first and second shield layers 12 and 15 are prevented
from deforming.
[0047] Preferably, the inner layer 12B and the inner layer 15B are
made of, for example, NiFeV, NiFeB, CoZrNb, CoZrTa, FeAlSi,
FeNiAlSi, FeN, FeAlN, FeZrN, FeZrC, FeZrBN, FeTaN or the like,
because these materials have magnetism and also have a high Vickers
hardness. Table 1 provides the exemplary compositions of materials
which are preferably used as the inner layers 12B and 15B. Table 1
also provides the Vickers hardness Hv for each composition, which
is obtained when each of the layers 12B and 15B is 500 nm in
thickness and is under an indentation load of 0.1 g.
1 TABLE 1 Composition (atom %) Vickers hardness Hv
Ni.sub.76Fe.sub.19V.sub.5 500 Ni.sub.76Fe.sub.19B.sub.5 500
Co.sub.83Zr.sub.8Nb.sub.9 750 Co.sub.85Zr.sub.6Ta.sub.9 780
Fe.sub.66Al.sub.14Si.sub.20 800 Fe.sub.64Ni.sub.2Al.sub.14Si.sub.20
800 Fe.sub.95N.sub.5 900 Fe.sub.92Al.sub.3N.sub.5 910
Fe.sub.84Zr.sub.8N.sub.8 1000 Fe.sub.84Zr.sub.8C.sub.8 1000
Fe.sub.84Zr.sub.5B.sub.3N.sub.8 1100 Fe.sub.83Ta.sub.7N.sub.10
1100
[0048] A thickness S1 of the inner layer 12B of the first shield
layer 12 is determined so that the sum of the thickness S1 and a
thickness G1 of the first gap film 13 is equal to or more than 40
nm. Thus, a distance of at least 40 nm is created between the MR
film 20 and the outer layer 12A, and therefore, even if the outer
layer 12A becomes deformed, the deformed outer layer 12A is hard to
extend to the MR film 20. Similarly, a thickness S2 of the inner
layer 15B of the second shield layer 15 is determined so that the
sum of the thickness S2 and a thickness G2 of the second gap film
14 is equal to or more than 40 nm. Thus, a distance of at least 40
nm is created between the MR film 20 and the outer layer 15A, and
therefore, even if the outer layer 15A becomes deformed, the
deformed outer layer 15A is hard to extend to the MR film 20. In
the embodiment, the thicknesses S1, G1, S2 and G2 are measured on
the air bearing surface 2E (see FIG. 5). An upper limit to the sum
(S1+G1) of the thickness S1 of the inner layer 12B and the
thickness G1 of the first gap film 13 and an upper limit to the sum
(S2+G2) of the thickness S2 of the inner layer 15B and the
thickness G2 of the second gap film 14 are appropriately determined
according to a linear recording density of the magnetic medium.
[0049] For example, each of the first and second gap films 13 and
14 is 10 nm to 100 nm in thickness and is made of Al.sub.2O.sub.3
or AlN (aluminum nitride). The first and second gap films 13 and 14
function to provide electrical insulation between the MR film 20 to
be described later and the first and second shield layers 12 and
15. For example, the insulating layer 16 is 10 nm to 100 nm in
thickness and is made of Al.sub.2O.sub.3 or AlN in the same manner
as the first and second gap films 13 and 14. The insulating layer
16 functions to provide electrical insulation between the
reproducing head 1A and the recording head 1B. In the embodiment,
the first gap film 13 corresponds to a specific example of "a first
gap film" or "a first insulating film" of the invention. The second
gap film 14 corresponds to a specific example of "a second gap
film" or "a second insulating film" of the invention.
[0050] An MR element 1C including the MR film 20 that is a spin
valve film is sandwiched in between the first gap film 13 and the
second gap film 14. The reproducing head 1A is adapted to read out
information recorded on the magnetic medium 3 through the use of
the electrical resistance of the MR film 20 changing according to a
signal magnetic field of the magnetic medium 3. In the embodiment,
the MR film 20 corresponds to a specific example of "a functional
film" of the invention.
[0051] FIG. 7 is a cross sectional view showing a sectional
structure of the MR film 20. The MR film 20 has a laminated
structure comprising an underlayer 21, a first soft magnetic layer
22A, a second soft magnetic layer 22B, a nonmagnetic layer 23, a
ferromagnetic layer 24, an antiferromagnetic layer 25 and a cap
layer 26, which are laminated in this order on the first gap film
13. For example, the underlayer 21 is 5 nm to 10 nm in thickness
and is made of Ta (tantalum).
[0052] For example, the first soft magnetic layer 22A is 1 nm to 3
nm in thickness and is made of a magnetic material containing at
least Ni in a group consisting of Ni (nickel), Co (cobalt) and Fe.
For example, the second soft magnetic layer 22B is 0.5 nm to 3 nm
in thickness and is made of a magnetic material containing at least
Co in a group consisting of Ni, Co and Fe. The first soft magnetic
layer 22A and the second soft magnetic layer 22B constitute a soft
magnetic layer 22 which is sometimes called a free layer, and the
soft magnetic layer 22 is adapted to change its orientation of
magnetization according to a signal magnetic field from the
magnetic medium 3.
[0053] For example, the nonmagnetic layer 23 is 1.8 nm to 3.0 nm in
thickness and is made of a nonmagnetic material containing at least
one element in a group consisting of Au (gold), Ag (silver), Cu
(copper), Ru (ruthenium), Rh (rhodium), Re (rhenium), Pt (platinum)
and W (tungsten). The nonmagnetic layer 23 functions to
magnetically isolate the soft magnetic layer 22 from the
ferromagnetic layer 24 and the antiferromagnetic layer 25 as much
as possible.
[0054] For example, the ferromagnetic layer 24 is 2 nm to 4.5 nm in
thickness and is made of a magnetic material containing at least Co
in a group consisting of Co and Fe. Preferably, the ferromagnetic
layer 24 is made of a magnetic material whose (111) plane is
oriented in the laminating direction. The ferromagnetic layer 24 is
sometimes called a pinned layer, and the orientation of
magnetization of the ferromagnetic layer 24 is fixed by exchange
coupling on an interface between the ferromagnetic layer 24 and the
antiferromagnetic layer 25. In the embodiment, the orientation of
magnetization of the ferromagnetic layer 24 is fixed in the
Y-direction (see FIG. 5).
[0055] For example, the antiferromagnetic layer 25 is 5 nm to 30 nm
in thickness and is made of an antiferromagnetic material
containing at least one element in a group consisting of Pt, Ru,
Rh, Pd (palladium), Ni, Au, Ag, Cu, Ir (iridium), Cr (chromium) and
Fe, and Mn. The antiferromagnetic layer 25 may be made of an
antiferromagnetic material containing at least one element in a
group consisting of Ni, Fe and Co, and O (oxygen).
[0056] Antiferromagnetic materials include a non-heat-treatment
type antiferromagnetic material which induces an exchange coupling
magnetic field between the antiferromagnetic material and a
ferromagnetic material without heat treatment, and a heat-treatment
type antiferromagnetic material which induces an exchange coupling
magnetic field between the antiferromagnetic material and a
ferromagnetic material with heat treatment. The antiferromagnetic
layer 25 may be made of either of the non-heat-treatment type
antiferromagnetic material and the heat-treatment type
antiferromagnetic material. Non-heat-treatment type
antiferromagnetic materials include a Mn alloy having y-phase, and
so forth. More specifically, RuRhMn (a ruthenium-rhodium-manganese
alloy), FeMn (an iron-manganese alloy), IrMn (an iridium-manganese
alloy) and the like are included. Heat-treatment type
antiferromagnetic materials include a Mn alloy having a regular
crystal structure, and so forth. More specifically, PtMn (a
platinum-manganese alloy), NiMn (a nickel-manganese alloy), PtRhMn
(a platinum-rhodium-manganese alloy) and the like are included.
[0057] For example, the cap layer 26 is 5 nm to 10 nm in thickness
and is made of Ta or the like. The cap layer 26 functions to
protect the MR film 20 in the process of manufacturing the thin
film magnetic head 1.
[0058] Magnetic domain control films 30A and 30B are provided on
both sides of the MR film 20 in a direction perpendicular to the
laminating direction. The magnetic domain control films 30A and 30B
are made of, for example, a hard magnetic material so as to
generate a bias magnetic field Hb to the MR film 20 in the
X-direction. The magnetic domain control films 30A and 30B generate
the bias magnetic field Hb and thus orient the magnetization of the
soft magnetic layer 22 of the MR film 20 in the direction of the
bias magnetic field Hb, thereby preventing the so-called Barkhausen
noise. For example, CoPt (cobalt-platinum), CoPtCr
(cobalt-platinum-chromium), NdFeB (neodymium-iron-boron), SmCo
(samarium-cobalt) or the like can be used as the hard magnetic
material of which the magnetic domain control films 30A and 30B are
made.
[0059] Lead layers 33A and 33B made of, for example, Ta are
provided on the magnetic domain control films 30A and 30B,
respectively. The lead layers 33A and 33B are connected to
terminals 33C and 33D, respectively, through openings (not shown)
formed in the second gap film 14 and the insulating layer 16. Thus,
a current can be fed through the MR film 20 via the lead layers 33A
and 33B.
[0060] For example, as shown in FIGS. 3 and 5, the recording head
1B has a bottom pole 41 of 0.5 .mu.m to 3 .mu.m thick made of a
magnetic material such as NiFe, which is formed on the insulating
layer 16 of the reproducing head 1A. A write gap film 42 of 0.05
.mu.m to 0.3 .mu.m thick made of Al.sub.2O.sub.3 or the like is
formed on the bottom pole 41. The write gap film 42 has an opening
42A at a position corresponding to the center of thin film coils 44
and 46 to be described later. An insulating layer 43, which is made
of Al.sub.2O.sub.3 or the like and has a thickness of 1.0 .mu.m to
5.0 .mu.m for determining a throat height, is formed on the write
gap film 42. The thin film coil 44 of 1 .mu.m to 3 .mu.m thick and
a photoresist layer 45 for coating the thin film coil 44 are formed
on the insulating layer 43. The thin film coil 46 of 1 .mu.m to 3
.mu.m thick and a photoresist layer 47 for coating the thin film
coil 46 are formed on the photoresist layer 45. In the embodiment,
the description is given with regard to an example in which two
thin film coil layers are laminated, but the number of thin film
coil layers may be one, or three or more.
[0061] A top pole 48 of about 3 .mu.m thick made of a magnetic
material having a high saturation magnetic flux density, such as
NiFe or FeN (iron nitride), is formed on the write gap film 42, the
insulating layer 43 and the photoresist layers 45 and 47. The top
pole 48 is in contact with and magnetically coupled to the bottom
pole 41 through the opening 42A of the write gap film 42 formed at
the position corresponding to the center of the thin film coils 44
and 46. Although not shown in FIGS. 3 to 5, an overcoat layer (an
overcoat layer 49 shown in FIG. 15) of 20 .mu.m to 30 .mu.m thick
made of, for example, Al.sub.2O.sub.3 is formed on the top pole 48
so as to coat the overall surface. In the embodiment, a laminar
structure including the portions 41 to 49 corresponds to the
recording head 1B. The recording head 1B generates a magnetic flux
between the bottom pole 41 and the top pole 48 by a current passing
through the thin film coils 44 and 46, and thus magnetizes the
magnetic medium 3 by the magnetic flux generated near the write gap
film 42, thereby recording information on the magnetic medium
3.
[0062] <Operation of MR Element and Thin Film Magnetic
Head>
[0063] Next, a reproducing operation of the thin film magnetic head
1 configured as described above will be described with main
reference to FIGS. 6 and 7.
[0064] In the thin film magnetic head 1, the reproducing head 1A
reads out information recorded on the magnetic medium 3. In the
reproducing head 1A, the orientation of magnetization of the
ferromagnetic layer 24, for example, is fixed in the Y-direction by
exchange coupling on the interface between the ferromagnetic layer
24 and the antiferromagnetic layer 25 of the MR film 20. The
magnetization of the soft magnetic layer 22 is oriented in the same
direction as the direction of the bias magnetic field Hb (the
X-direction in the embodiment) by the bias magnetic field Hb
generated by the magnetic domain control films 30A and 30B. The
orientation of the bias magnetic field Hb is substantially
perpendicular to the orientation of magnetization of the
ferromagnetic layer 24. To read out information, a sense current
that is a stationary electric current is fed through the MR film 20
through the lead layers 33A and 33B in the direction of the bias
magnetic field Hb, for example.
[0065] Many data elements (each of which is an area corresponding
to 1 bit of data) are arranged at regular intervals in the
Z-direction on the track line of the magnetic medium 3. A distance
between the first and second shield layers 12 and 15 of the thin
film magnetic head 1 corresponds to a distance between two data
elements on the track line of the magnetic medium 3. When the MR
film 20 of the thin film magnetic head 1 faces one data element,
magnetic fluxes from other data elements flow through the first and
second shield layers 12 and 15, but the magnetic fluxes can hardly
flow through the MR film 20. Moreover, a magnetic flux generated by
the thin film coils 44 and 46 of the recording head 1B flows
through the second shield layer 15, but the magnetic flux can
hardly flow through the MR film 20. This prevents an undesired
magnetic field from reaching to the MR film 20.
[0066] In the MR film 20 of the thin film magnetic head 1, the
orientation of magnetization of the soft magnetic layer 22 changes
according to a signal magnetic field of the magnetic medium 3. On
the other hand, the orientation of magnetization of the
ferromagnetic layer 24 does not change because the orientation
thereof is fixed by exchange coupling between the ferromagnetic
layer 24 and the antiferromagnetic layer 25. When the orientation
of magnetization of the soft magnetic layer 22 changes, a current
passing through the MR film 20 is subjected to resistance according
to a relative angle between the orientation of magnetization of the
soft magnetic layer 22 and the orientation of magnetization of the
ferromagnetic layer 24. This results from a phenomenon that is
called "spin-dependent scattering": that is, the degree of
scattering of electrons on an interface between a nonmagnetic layer
and a magnetic layer depends on the direction of magnetization of
the magnetic layer. The amount of change in resistance of the MR
film 20 is detected as the amount of change in voltage, and thus,
information recorded on the magnetic medium 3 is read out.
[0067] In the embodiment, the first shield layer 12 and the second
shield layer 15 have the outer layer 12A and the outer layer 15A,
respectively, which are made of a material having high thermal
conductivity. Therefore, heat generated by the MR film 20 is
efficiently diffused via the outer layer 12A and the outer layer
15A. In other words, deterioration in performance incident to an
excessive rise in temperature of the MR film 20 is prevented.
[0068] <Method of Manufacturing thin Film Magnetic Head>
[0069] Next, a method of manufacturing the MR element 1C and the
thin film magnetic head 1 will be described with reference to FIGS.
8 to 15. FIGS. 8 to 15 show a sectional structure taken along the
line V-V of FIG. 4.
[0070] In the manufacturing method according to the embodiment,
first of all, as shown in FIG. 8, for example, the insulating layer
11 is formed on one surface of the base 2D made of
Al.sub.2O.sub.3--TiC by means of sputtering using the material
mentioned in the description of the configuration. Then, the outer
layer 12A of the first shield layer 12 is formed on the insulating
layer 11 by means of, for example, plating using the material
mentioned in the description of the configuration. Then, the inner
layer 12B is formed on the outer layer 12A by means of, for
example, sputtering using the material mentioned in the description
of the configuration. After that, the outer layer 12A and the inner
layer 12B are patterned into a shape shown in FIG. 3 by means of
ion milling.
[0071] Then, as shown in FIG. 9, the underlayer 21, the first soft
magnetic layer 22A, the second soft magnetic layer 22B, the
nonmagnetic layer 23, the ferromagnetic layer 24, the
antiferromagnetic layer 25 and the cap layer 26 are formed in
sequence on the first shield layer 12 by means of, for example,
sputtering using the materials mentioned in the description of the
configuration, and thus the MR film 20 is formed. After that, as
shown in FIG. 10, a photoresist film 51 for patterning is
selectively formed on the MR film 20. After forming the photoresist
film 51, the MR film 20 is etched by means of, for example, ion
milling using the photoresist film 51 as a mask, and thus the MR
film 20 having a shape shown in FIG. 7 is formed.
[0072] After patterning the MR film 20, the magnetic domain control
films 30A and 30B shown in FIG. 7 are formed on both sides of the
MR film 20 by means of, for example, sputtering using the hard
magnetic material mentioned in the description of the
configuration. After that, the lead layers 33A and 33B shown in
FIG. 7 are formed on the magnetic domain control films 30A and 30B,
respectively, by means of sputtering using the material mentioned
in the description of the configuration. After that, the
photoresist film 51 and a deposit laminated on the photoresist film
51 are removed by means of lift-off procedures, for example.
[0073] After lift-off procedures, as shown in FIG. 11, the second
gap film 14 is formed by means of, for example, sputtering using
the material mentioned in the description of the configuration, so
as to coat the first gap film 13 and the MR film 20. Thus, the MR
film 20 is sandwiched in between the first gap film 13 and the
second gap film 14. After that, as shown in FIG. 12, the inner
layer 15B of the second shield layer 15 is formed on the second gap
film 14 by means of, for example, sputtering using the material
mentioned in the description of the configuration. After that, a
part of the outer layer 15A is formed on the inner layer 15B by
means of sputtering, for example. In this case, the outer layer
15A, which is to have a thickness of 2 .mu.m, is formed with a
thickness of, for example, only 30 nm by means of sputtering. Then,
as shown in FIG. 13, the remaining part (of about 2 .mu.m thick) of
the outer layer 15A is formed by means of plating using as an
electrode the part of the outer layer 15A formed by means of
sputtering. After forming the outer layer 15A of the second shield
layer 15, the second shield layer 15 is patterned into a shape
shown in FIG. 3 by means of ion milling.
[0074] After patterning the second shield layer 15, the insulating
layer 16 is formed by means of, for example, sputtering using the
material mentioned in the description of the configuration. After
forming the insulating layer 16, as shown in FIG. 14, the bottom
pole 41 is formed on the insulating layer 16 by means of, for
example, sputtering using the material mentioned in the description
of the configuration. Then, the write gap film 42 is formed on the
bottom pole 41 by means of, for example, sputtering, and then the
insulating layer 43 is formed into a predetermined pattern on the
write gap film 42. After forming the insulating layer 43, the thin
film coil 44 is formed on the insulating layer 43 by using the
material mentioned in the description of the configuration, and
then the photoresist layer 45 is formed into a predetermined
pattern so as to coat the thin film coil 44. After forming the
photoresist layer 45, the thin film coil 46 is formed on the
photoresist layer 45 by using the material mentioned in the
description of the configuration, and then the photoresist layer 47
is formed into a predetermined pattern so as to coat the thin film
coil 46.
[0075] After forming the photoresist layer 47, as shown in FIG. 15,
for example, the write gap film 42 is partly etched at the position
corresponding to the center of the thin film coils 44 and 46, and
thus the opening 42A for forming a magnetic path is formed. After
that, for example, the top pole 48 is formed on the write gap film
42, the opening 42A, the insulating layer 43 and the photoresist
layers 45 and 47 by using the material mentioned in the description
of the configuration. After forming the top pole 48, for example,
the write gap film 42 and the bottom pole 41 are selectively etched
by means of ion milling using the top pole 48 as a mask. After
that, the overcoat layer 49 is formed on the top pole 48 by using
the material mentioned in the description of the configuration.
[0076] After forming the overcoat layer 49, for example, heat
treatment takes place to induce exchange coupling between the
ferromagnetic layer 24 and the antiferromagnetic layer 25 of the MR
film 20. More specifically, the thin film magnetic head 1 is heated
at a blocking temperature of the antiferromagnetic layer 25 and the
ferromagnetic layer 24 in a state in which a magnetic field is
applied in, for example, the Y-direction by use of a magnetic field
generating apparatus or the like. Thus, the orientation of
magnetization of the ferromagnetic layer 24 is fixed in the
direction Y of the applied magnetic field by exchange coupling
between the ferromagnetic layer 24 and the antiferromagnetic layer
25.
[0077] Finally, for example, the air bearing surface 2E of the
slider 2 is polished, and thus the thin film magnetic head 1 is
completed. In the step of polishing the slider 2, the first and
second shield layers 12 and 15 have the inner layers 12B and 15B
having higher hardness, respectively, which are located close to
the MR film 20, and therefore the first and second shield layers 12
and 15 are prevented from deforming and thus coming into contact
with the MR film 20.
[0078] <Advantages of Embodiment>
[0079] As described above, according to the embodiment, the first
and second shield layers 12 and 15 have the inner layers 12B and
15B having higher hardness, respectively, which are located close
to the MR film 20. In the step of polishing the air bearing surface
2E, the first and second shield layers 12 and 15 are therefore
prevented from deforming and thus coming into contact with the MR
film 20. This allows preventing a contact of the first and second
shield layers 12 and 15 with the MR film 20 and thus permits
preventing an output decrease of the thin film magnetic head 1,
even when the distance between the first and second shield layers
12 and 15 is reduced in order to increase a linear recording
density.
[0080] More particularly, the sum of the thickness S1 of the inner
layer 12B of the first shield layer 12 and the thickness G1 of the
first gap film 13 is equal to or more than 40 nm, and the sum of
the thickness S2 of the inner layer 15B of the second shield layer
15 and the thickness G2 of the second gap film 14 is equal to or
more than 40 nm. Even when the outer layers 12A and 15A become
deformed, the deformed outer layers 12A and 15A are therefore hard
to come into contact with the MR film 20.
[0081] Furthermore, the inner layers 12B and 15B have a Vickers
hardness Hv of 500 or higher, so that this can further ensure that
the first and second shield layers 12 and 15 are prevented from
deforming, and therefore this can further ensure that the first and
second shield layers 12 and 15 are prevented from coming into
contact with the MR film 20.
[0082] Moreover, the outer layers 12A and 15A are provided in the
embodiment, and therefore the embodiment facilitates patterning
using ion milling or the like, as compared to the case where the
whole first and second shield layers 12 and 15 are made of a
material having high hardness. Accordingly, the thin film magnetic
head can be manufactured in a shorter time.
[0083] In addition, the outer layers 12A and 15A are made of a
material having high thermal conductivity, and therefore, heat
generated by the MR film 20 can be efficiently diffused, so that
this can prevent deterioration in performance due to the heat of
the MR film 20.
[0084] Additionally, each of the inner layers 12B and 15B has a
thickness of 300 nm or less, and therefore the time required for
ion milling or the like of the first and second shield layers 12
and 15 is relatively short.
[0085] Moreover, the outer layers 12A and 15A are made of NiFe, and
therefore the outer layers 12A and 15A can obtain high magnetic
permeability, so that an undesired magnetic flux can flow through
the outer layers 12A and 15A so as not to flow through the MR film
20. In other words, the effect of preventing an undesired magnetic
field from reaching to the MR film 20 can be enhanced.
[0086] <Modified Embodiments>
[0087] FIG. 16 shows a sectional structure of a thin film magnetic
head 101 according to a modified embodiment. In the thin film
magnetic head 101 according to the modified embodiment, a first
shield layer 120 comprises an outer layer 120A and an inner layer
120B, and the inner layer 120B is locally formed only in a region
near the air bearing surface 2E. Similarly, a second shield layer
150 comprises an outer layer 150A and an inner layer 150B, and the
inner layer 150B is locally formed only in a region near the air
bearing surface 2E.
[0088] In the modified embodiment, the inner layers 120B and 150B
are only locally formed, but, at least in the air bearing surface
2E, the MR film 20 is sandwiched in between the first and second
gap films 13 and 14, which are sandwiched in between the inner
layers 120B and 150B. In the step of polishing the air bearing
surface 2E, the first and second shield layers 120 and 150 are
therefore prevented from deforming and thus prevented from coming
into contact with the MR film 20, as in the case of the
above-described embodiment.
[0089] The inner layers 120B and 150B may be locally formed in the
X-direction in FIG. 6, for example. In this case, the inner layers
120B and 150B are formed at a position at which at least the MR
film 20 is sandwiched in between the inner layers 120B and 150B in
the laminating direction, and thus the first and second shield
layers 120 and 150 are prevented from coming into contact with the
MR film 20, as in the case of the above-described embodiment and
modified embodiment.
EXAMPLES
[0090] Next, specific examples of the invention will be described
in detail.
Example 1
[0091] Ten types of thin film magnetic heads 1 shown in FIG. 5 were
made as an example 1, and the respective inner layers 12B and 15B
of the first and second shield layers 12 and 15 had varying
thicknesses. Each thin film magnetic head 1 was made in the
following manner. First, the insulating layer 11 of 2 .mu.m thick
was formed of Al.sub.2O.sub.3 on the base 2D made of
Al.sub.2O.sub.3--TiC by means of sputtering, and the outer layer
12A of 2 .mu.m thick of the first shield layer 12 was formed of
Ni.sub.80Fe.sub.20 on the insulating layer 11 by means of plating.
After that, the inner layer 12B was formed of
Fe.sub.84Zr.sub.8N.sub.8 on the outer layer 12A of the first shield
layer 12 by means of sputtering. The inner layers 12B had
thicknesses varying from 5 nm to 50 nm at intervals of 5 nm. Then,
the first gap film 13 of 10 nm thick was formed of Al.sub.2O.sub.3
on the inner layer 12B of the first shield layer 12 by means of,
for example, sputtering.
[0092] Then, the underlayer 21 of 5 nm thick was formed of Ta on
the first gap film 13 by means of sputtering, the first soft
magnetic layer 22A of 3 nm thick was formed of NiFe on the
underlayer 21, and the second soft magnetic layer 22B of 1 nm thick
was formed of CoFe on the first soft magnetic layer 22A. Then, the
nonmagnetic layer 23 of 2.5 nm thick was formed of Cu on the second
soft magnetic layer 22B by means of sputtering, the ferromagnetic
layer 24 of 2 nm thick was formed of CoFe on the nonmagnetic layer
23, the antiferromagnetic layer 25 of 20 nm thick was formed of
PtMn on the ferromagnetic layer 24, and the cap layer 26 of 5 nm
thick was formed of Ta on the antiferromagnetic layer 25. After
forming the cap layer 26, heat treatment took place to subject the
antiferromagnetic layer 25 to an antiferromagnetizing process.
[0093] Then, a laminated film including the layers 21 to 26 was
patterned by means of ion milling, and thus the MR film 20 having a
shape shown in FIG. 6 was formed. Then, the magnetic domain control
films 30A and 30B each having a thickness of 50 nm were formed of
CoPt on both sides of the MR film 20 by means of, for example,
sputtering, and the lead layers 33A and 33B each having a thickness
of 100 nm were formed into a predetermined shape on the magnetic
domain control films 30A and 30B, respectively, by means of, for
example, sputtering.
[0094] After forming the lead layers 33A and 33B, the second gap
film 14 of 10 nm thick was formed of Al.sub.2O.sub.3 by means of
sputtering so as to coat the MR film 20, the magnetic domain
control films 30A and 30B and the lead layers 33A and 33B. Then,
the inner layer 15B of the second shield layer 15 was formed of
Fe.sub.84Zr.sub.8N.sub.8 on the second gap film 14 by means of
sputtering. The inner layers 15B had thicknesses varying from 5 nm
to 50 nm at intervals of 5 nm. Then, a 30-nm-thick part of the
outer layer 15A was formed of Ni.sub.80Fe.sub.20 on the inner layer
15B by means of sputtering. Then, the outer layer 15A of 2 .mu.m
thick was formed of Ni.sub.80Fe.sub.20 by means of plating using
the 30-nm-thick part of the outer layer 15A as an electrode
film.
[0095] The insulating layer 16, the bottom pole 41, the write gap
film 42, the insulating layer 43, the thin film coil 44, the
photoresist layer 45, the thin film coil 46, the photoresist layer
47, the top pole 48 and the overcoat layer 49 shown in FIG. 5 were
laminated on the second shield layer 15. Since the structure
including the portions 16 and 41 to 49 (i.e., the recording head
1B) has no influence on items of the example to be measured, the
detailed description thereof is omitted. A sufficient number of
thin film magnetic heads 1 of each type were made to check the
fraction defective.
Example 2
[0096] Ten types of thin film magnetic heads 1 shown in FIG. 5 were
made as an example 2 similarly to the example 1, that is, ten types
of thin film magnetic heads 1 of each of the examples 1 and 2 were
made. However, both of the first and second gap films 13 and 14 had
a thickness of 20 nm. As in the case of the example 1, the
respective inner layers 12B and 15B of the first and second shield
layers 12 and 15 had thicknesses varying from 5 nm to 50 nm at
intervals of 5 nm. As in the case of the example 1, a sufficient
number of thin film magnetic heads 1 of each type were made to
check the fraction defective.
[0097] The resistance of the MR film 20 of each of twenty types of
thin film magnetic heads 1 made as described above was measured,
the number of thin film magnetic heads having resistance values
that were 10% or more lower than a predetermined reference
resistance value was counted, and the rate of the counted thin film
magnetic heads was calculated as the fraction defective. The
reference resistance value was set in the following manner: that
is, a thin film magnetic head having no first and second shield
layers 12 and 15 (i.e., a thin film magnetic head having a
structure in which the MR film 20 was sandwiched directly in
between the insulating layers 11 and 16) was formed, and a
resistance value of the MR film of the thin film magnetic head was
measured.
[0098] [Comparisons 1 and 2]
[0099] As comparisons to the examples, thin film magnetic heads
were made under the same conditions as the conditions for the
examples 1 and 2, except that the respective inner layers 12B and
15B of the first and second shield layers 12 and 15 were not
provided. The fraction defective of the comparisons 1 and 2 is also
shown in FIG. 17.
[0100] As can be seen from FIG. 17, when the example 1 having the
first and second gap films 13 and 14 each having a thickness of 10
nm is compared to the comparison 1, it has been shown that the
example 1 having the inner layers 12B and 15B can be reduced in
fraction defective, as compared to the comparison 1 having no inner
layers 12B and 15B. It has been shown that the fraction defective
can become approximately 0, particularly when each of the inner
layers 12B and 15B has a thickness of 30 nm or more.
[0101] When the example 2 having the first and second gap films 13
and 14 each having a thickness of 20 nm is compared to the
comparison 2, it has been shown that the example 2 having the inner
layers 12B and 15B can be reduced in fraction defective, as
compared to the comparison 2 having no inner layers 12B and 15B. It
has been shown that the fraction defective can become approximately
0, particularly when each of the inner layers 12B and 15B has a
thickness of 20 nm or more.
[0102] In the example 1, the fraction defective can become
approximately 0 when each of the inner layers 12B and 15B has a
thickness of 30 nm or more. In the example 2, the fraction
defective can become approximately 0 when each of the inner layers
12B and 15B has a thickness of 20 nm or more. Therefore, it has
been shown that the fraction defective can become approximately 0
when the sum (S1+G1) of the thickness S1 of the inner layer 12B and
the thickness G1 of the first gap film 13 is equal to or more than
40 nm or when the sum (S2+G2) of the thickness S2 of the inner
layer 15B and the thickness G2 of the second gap film 14 is equal
to or more than 40 nm.
[0103] Although the invention is described above by referring to
the embodiment and examples, the invention is not limited to these
embodiment and examples and various modifications of the invention
are possible. For example, in the above-described embodiment, both
of the first and second shield layers 12 and 15 have the inner
layer and the outer layer, but only either the first or second
shield layer 12 or 15 may have the inner layer and the outer
layer.
[0104] In the above-described embodiment, the antiferromagnetic
layer 25 of the MR film 20 is made of a heat-treatment type
antiferromagnetic material, but the antiferromagnetic layer 25 may
be made of a non-heat-treatment type antiferromagnetic material. In
this case, exchange coupling can be induced on the interface
between the antiferromagnetic layer 25 and the ferromagnetic layer
24 without heat treatment.
[0105] In the above-described embodiment, the magnetic domain
control films 30A and 30B are made of a hard magnetic material, but
the magnetic domain control films 30A and 30B may have a laminated
structure comprising an antiferromagnetic film and a ferromagnetic
film. When the antiferromagnetic film is made of a heat-treatment
type antiferromagnetic material, heat treatment is necessary to
induce exchange coupling between the antiferromagnetic film and the
ferromagnetic film. When the antiferromagnetic film is made of a
non-heat-treatment type antiferromagnetic material, heat treatment
is not necessary.
[0106] The MR film of the thin film magnetic head 1 is not limited
to the spin valve film, and the MR film may be any of other types
of films such as a GMR film, an AMR film and a TMR (tunnel-type
magnetoresistive) film. The thin film magnetic head 1 may be a head
for reproducing only, a magnetic sensor or a memory.
[0107] As described above, according to the thin film magnetic head
of the invention or the method of manufacturing a thin film
magnetic head of the invention, at least one of the first and
second shield layers has the inner layer and the outer layer, and
the inner layer having higher hardness is located close to a
magnetic layer. Therefore, in the step of polishing or the like, at
least one of the first and second shield layers becomes resistant
to deformation. This allows preventing a contact of the first and
second shield layers with the functional film and therefore permits
preventing an output decrease of the thin film magnetic head, even
when the distance between the first and second shield layers is
reduced in order to increase the linear recording density.
Furthermore, the outer layer having lower hardness than the
hardness of the inner layer is provided, and therefore the shield
layer can undergo patterning or the like in a shorter time, as
compared to a shield layer which is wholly made of a high-hardness
material, so that deterioration in productivity can be prevented.
Furthermore, a material having high thermal conductivity is
selected as the outer layer, and thus the thermal conductivity of
at least one of the first and second shield layers can be also
improved. Therefore, heat generated by the functional film can be
efficiently diffused, so that deterioration in performance incident
to an excessive rise in temperature of the functional film can be
prevented. In other words, it is possible to prevent an output
decrease of the thin film magnetic head without impairment of
productivity and other characteristics, as well as to adapt to an
increase in the linear recording density.
[0108] According to the thin film magnetic head of the invention,
the sum of the thickness of the first gap film and the thickness of
the inner layer of the first shield layer is equal to or more than
40 nm, or the sum of the thickness of the second gap film and the
thickness of the inner layer of the second shield layer is equal to
or more than 40 nm. Therefore, this can further ensure that the
first and second shield layers are prevented from coming into
contact with the functional film.
[0109] According to the thin film magnetic head of the invention,
the Vickers hardness of the inner layer is equal to or higher than
500. Therefore, the first or second shield layer becomes more
resistant to deformation, so that this can further ensure that the
first and second shield layers are prevented from coming into
contact with the functional film.
[0110] According to the thin film magnetic head of the invention,
the thickness of the inner layer is equal to or less than 300 nm,
and therefore the time required for patterning or the like can be
such that the productivity of the thin film magnetic head does not
deteriorate.
[0111] According to the thin film magnetic head of the invention,
the outer layer is made of a material containing Ni and Fe.
Therefore, high magnetic permeability can be obtained, so that the
effect of preventing an undesired magnetic field from reaching to
the functional film can be enhanced.
[0112] Obviously many modifications and variations of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
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